Thin SiO_2 films have been deposited by electron beam evapouration method.The influences of oxygen partial pressure on the mechanical,surface morphology and optical properties were studied.The results show that the residual stress in the SiO_2 films varied from compressive stress to tensile stress with the oxygen partial pressure increase,which may be attributed to the evolution of the microstructure.At the same time,the surface roughness became larger and the refractive index decreased with the increase of the oxygen pressure.